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Topic: The best clock bearings so far. (Read 7647 times)

Hi everyone. I'm new here and I'm relatively new to building clocks. The first one I did was all wood according to Brian Law's plans. The second one was Brian's plans with some modifications. The third one was my design. I used 1/8" brass rod for the second had, 1/4" wood tubing for the minute hand and added brass clock chain winder instead of Brian's rope and pulley design. Now, I'm in the process of experimenting with bearings. I'm going to post some videos on youtube and I'll add the link here later. The best bearings I've found so far are using a steel shaft with pointed ends on about a 30 deg angle which fit into two brass screws, one at each end, that have a cup point on them at about 45 degrees. That gives you a point contact that is almost friction-less. My goal is to reduce the amount of weight needed to drive the gear train so I can make an 8 day clock.

Welcome to the forum. Thanks for sharing the experiments on bearings. Am interested in seeing the youtube videos once posted...

With respect to an 8-day clock, am also interested in the gear train you end up with. I was working on a 8 day clock (which I never completed), and could get the escapement wheel to initiate spin through the going train with the weight of 4 coke cans (~3.5 lbs). I used racer bearings though (ie, sealed ball bearings), primarily because I was concerned that to drive the great wheel would require a lot of weight, and the subsequent torque would put a lot of pressure and wear on the first few arbor bushings. Also, due to the size of the wheels (largest were 96 teeth) and the compartment I was trying to squeeze it into, I ended up with triangular shaped teeth rather than the traditional cycloidal gears...

That is a very nice looking clock. Are the wheels made out of solid wood?

I wonder how the pointed tip will wear compared to a small pinion. Do you really need to reduce the friction to near zero at the small end when there is still wood to wood friction at the teeth. Clocks have been designed with small diameter polished steel pinions and brass bushings for centuries. I think I will try ball bearings with the grease washed out for my next clock.

Steve,The wheels are made of solid cherry. As to the gear friction, with cycloidal gears, theoretically at least, there is only rolling friction. My reasoning was that the friction from shaft bearings is multiplied 60 times in the last shaft. You have rolling friction and also have to overcome starting friction each time the escapement stops and starts. The first test in the video using a 60 tooth gear, I have been able to get it to spin for 3 minutes. You can use that as a bench mark and see if you can get the same results with washed roller bearings. I did do a test with some small roller bearings, but haven't washed them yet. I will try that for a comparison.

It seems like washed roller or ball bearings would have only rolling resistance. There is a very slight rubbing at the sides, but this is unloaded so the effect should be minor.

My guess is that washed ball bearings would work best for the shaft supporting the drive weight and maybe even the pendulum. They probably would have been used in old clocks if high quality ball bearings were available centuries ago.

The slower wheels like the hour hand could use anything because they are geared down so much. Even burnished wood on wood should still be OK.

Ingenious! When you first mentioned the concept, I had it in mind that the "bushing cup" was being drilled out of the head of the screw, not the tail. Your solution appears to provide for ease of initial adjustment, and room for future maintenance should the arbor or screw "bushing" need to be reground due to normal wear...

Am still interested in your 8-day gear train. I came up with an 8-day gear train solution (which I will post in the "Wheels and Pinions" section), but I seem to require many more teeth than the train in your video...

Jon

P.S. By the way, I also took a peek at your other youtube videos, and am impressed by the grandfather clock, housing the wooden works in glass in a very traditional setting. Very nice!

On the escapement shaft, I also have a 38 tooth gear to a 38 tooth gear on the main shaft for the second hand. From the main shaft (minute hand shaft, I used a 15:60 (4:1) to drive the weight shaft. I have a chain on the weight shaft that is around a .625" shaft. So, The weight shaft will turn once for every 4 revolutions of the minute shaft or one turn every 4 hours. pi x .625 = 3.14159 x .625 = 1.96" every 4 hours. If the clock hangs 6' off the ground to the bottom of the weight that gives us 60 x 4 = 240 / 1.96 = 122 hours/24 = 5.1 days. I plan on putting a pulley on the weight which will double that time. Hope this helps.

I have used about every kind of bearing I could think of but the ones that work best were simply stainless pivots in brass bushings. My oldest clock has these and it has been running well for about 20 years. I do have to oil it every 7 or 8 years. I am trying ss pivots in delrin bushes now but don't have an opinion yet. I see a problem with pointed pivots in cups being that the whole clock, being made of wood, will change shape all the time and that style of bearing needs very close tolerances. For wheels and pinions, I use shop made plywood from veneer and epoxy, vacuum pressed and they are very strong and stable. but the plates are always moving in and out with the weather. I would like to use Lignum Vitae but the variety that is available is not the same as Harrison used and it gums up after a couple of months. I have used ball bearings a lot and they do pretty well but with no shields, they get dust in the races and the shields add friction.